Fell, H. B., J. Wyatt Durham, and D. L. Pawson. “Part U, Echinodermata 3, Vol. 1 & 2, Ch. 4, P. 367-491”. Treatise on Invertebrate Paleontology (January 1, 1966). Accessed December 4, 2024. https://journals.ku.edu/InvertebratePaleo/article/view/5656.